Do not use -Wl,no-undefined when using sanitizers

[Salamandar]

https://clang.llvm.org/docs/AddressSanitizer.html#id3

Right now, i've got lots of undefined references to the sanitizer runtime when linking the shared library.

[jpakkane]

Starting with 0.47.0 we print a warning about this if the project has these settings.

[thmo]

On Fedora 28, with meson 0.47.1 and clang 6.0.1, I still see undefined references when enabling sanitizers, unless I also set b_lundef=false.

[jeandet]

@jpakkane are you sure about the warning?

[0/1] /usr/bin/python3 /usr/bin/meson --internal regenerate /home/jeandet/Documents/prog/testubsan-meson /home/jeandet/Documents/prog/testubsan-meson/build --backend ninja
The Meson build system
Version: 0.47.1
Source dir: /home/jeandet/Documents/prog/testubsan-meson
Build dir: /home/jeandet/Documents/prog/testubsan-meson/build
Build type: native build
Project name: clang-ubsan
Project version: undefined
Native C compiler: clang (clang 6.0.1 "clang version 6.0.1 (tags/RELEASE_601/final)")
Build machine cpu family: x86_64
Build machine cpu: x86_64
Build targets in project: 3
Found ninja-1.8.2 at /usr/bin/ninja
[1/1] clang  -o libexe.so 'exe@sha/main.c.o' -fsanitize=undefined -Wl,--no-undefined -Wl,--as-needed -shared -fPIC -Wl,--start-group -Wl,-soname,libexe.so libfoo.a -Wl,--end-group  
FAILED: libexe.so 
clang  -o libexe.so 'exe@sha/main.c.o' -fsanitize=undefined -Wl,--no-undefined -Wl,--as-needed -shared -fPIC -Wl,--start-group -Wl,-soname,libexe.so libfoo.a -Wl,--end-group  
libfoo.a(foo.c.o) : Dans la fonction « foo » :
/home/jeandet/Documents/prog/testubsan-meson/build/../foo.c:4 : référence indéfinie vers « __ubsan_handle_nonnull_arg »
clang-6.0: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

[nirbheek]

The PR for this was #3770. If it does not work, that needs to be fixed.